1. Field of the Invention
This invention relates to an oxygen concentration controlling apparatus for adjusting the oxygen concentration in an elevator, a vegetable compartment of a refrigerator or the like, and a humidity controlling apparatus for controlling humidities in a sealed vessel.
2. Description of the Related Art
FIG. 1 is a structural diagram of an electrochemical oxygen concentration controller disclosed, for instance, in the Japanese Patent Publication No. 2-44764 (1990). In FIG. 1, references 1-13 represent the follows, respectively; 1 an anode, 2 a cathode, 3 a solid polymer electrolyte film, 4a, 4b collectors, 5 an oxygen enriched chamber, 6 an oxygen deficient chamber, 7 a gas inlet to the oxygen enriched chamber 5, 8 a gas output from the oxygen enriched chamber 5, 9 a gas inlet to the oxygen deficient chamber 6, 10 a gas output from the oxygen deficient chamber 6, 11 a generative water tank, 12 a supply water tank and 13 a pump. The word "oxygen deficient" referred to above means to reduce the oxygen concentration in a gas. To the contrary, the word "oxygen enriched" stands for increasing of the oxygen concentration in a gas. NAFION-117 a copolymeric perfluorocarbon with ion exchange groups (trade name of E. I. du Pont de Nemours and Co.) is used for the solid polymer electrolyte film 3. The nominal thickness of the solid polymer electrolyte film 3 is 7 mil, i.e., approximately 170 .mu.m, and the shortest distance between the anode and cathode is 150 .mu.m or so.
The above electrochemical oxygen concentration controller operates in a manner as follows.
The water is electrolyzed by the external power in the anode 1, whereby a reaction according to a formula (1) takes place, thus increasing the oxygen concentration in the oxygen enriched chamber 5. EQU 2H.sub.2 O.fwdarw.O.sub.2 +4H.sup.+ +4e.sup.- ( 1)
Protons (H.sup.30 ) and electrons (e.sup.-) generated at this time are, respectively through the solid polymer electrolyte film and the external circuit, brought to the cathode, and consume the oxygen in the reaction according to a formula (2). As a result, the oxygen concentration in the oxygen deficient chamber 6 lowers. EQU O.sub.2 +4H.sup.+ +4e.sup.- .fwdarw.2H.sub.2 O (2)
The water of average three molecules or so is moved from the anode to the cathode along with the protons (H.sup.+). The excessive water is, together with the water generated in the reaction of the formula (2), further transferred to the cathode from the anode. Meanwhile, the anode requires water, and therefore it is necessary to transfer the water to the water supply tank 12 by the pump 13.
The above electrochemical oxygen concentration controller of FIG. 1 utilizing the oxygen deficient chamber is applied to a storehouse of vegetables and fruits or a vegetable compartment of a refrigerator, as revealed in the Japanese Patent Publication No. 55-25343 (1980).
On the other hand, an air conditioner is an example of the electrochemical oxygen concentration controller of a type using the oxygen enriched chamber to increase the oxygen concentration inside hospital rooms or the like.
As depicted before, the conventional electrochemical oxygen concentration controller needs two tanks, that is, the generative water tank 11 and the water supply tank 12, and moreover it necessitates to transfer water by means of the pump 13.
FIG. 2 is a cross section showing the structure of a conventional oxygen concentration controlling apparatus disclosed, for example, in the Japanese Patent Publication No. 63-52119 (1988). Referring to FIG. 2, an oxygen concentration controlling element 60 is hermetically disposed inside an insulating frame 50 and consists of a diaphragm 3 made of a proton conductive solid and first and second porous electrodes 1, 2 arranged at the surfaces of the diaphragm 3. First and second reaction chambers 5, 6 provided with first and second collectors 4a, 4b, respectively, are separated from each other by the oxygen concentration controlling element 60 in the frame 50. A voltage is added to the first and second collectors 4a, 4b from a direct current supply 14. At this time, the first collector 4a is charged positively. A supply tube 17 couples the second reaction chamber 6 with the atmospheric air. A first water tank 11 having a first communication port 11a in the lower part, a first discharge tube 11b at the ceiling and a first suction port 11c in the upper part, stores the water in a manner to leave a gas layer in the upper part. Similarly, a second water tank 12 provided with a second communication port 12a in the lower part, a water supply port 12d at the bottom, a second discharge tube 12b at the ceiling and a second suction port 12c in the upper part stores the water, with a gas layer remaining in the upper part. The first communication port 11a of the first water tank 11 is connected to the second communication port 12a of the second water tank 12 by a communication tube 22, and the second reaction chamber 6 is connected to the first suction port 11c of the first water tank 11 by a first suction tube 23. The first reaction chamber 5 is connected with the water supply port 12d of the second water tank 12 by a water supply tube 24, while the first reaction chamber 5 is connected with the second suction port 12c of the second water tank 12 by a second suction tube 25.
When operating the conventional oxygen concentration controlling apparatus in the above-discussed structure, first, the water is stored in the first and second water tanks 11, 12. The water level in the water tanks 11, 12 are held the same because the tanks 11, 12 communicate with each other via the communication tube 22. Subsequently, the water is supplied from the second water tank 12 to the first reaction chamber 5 through the water supply tube 24. On the other hand, to the second reaction chamber 6 is fed the oxygen through the supply tube 17 from outside. In this state, a voltage is impressed to the first and second collectors 4a, 4b from the direct current supply 14 as to charge the first collector 4a positively. Accordingly, the following reaction takes place at the interface between the first porous electrode 1 which is charged positively by the impressed voltage and the diaphragm 3 made of the proton conductive solid; EQU 2H.sub.2 O.fwdarw.4H.sup.+ +O.sub.2 +4e.sup.-
As a result of the reaction, the water supplied to the first reaction chamber 5 is electrolyzed to produce the oxygen. The produced oxygen passes through the second suction tube 25 to the second water tank 12 together with the water left without reacting. As the oxygen and water are separated in the second water tank 12, only the water is stored in the second water tank 12, and the oxygen is discharged from the second discharge tube 12b to be fed to the atmosphere which is necessary to be enriched as in an elevator, etc.
The hydrogen ions generated in the above reaction move through the diaphragm 3 toward the negatively charged second porous electrode 2. When the hydrogen ions reach the second porous electrode 2, it brings about the following reaction at the interface between the second porous electrode 2 and the diaphragm 3 of a proton conductive solid; EQU 4H.sup.+ +O.sub.2 +4e.sup.- .fwdarw.2H.sub.2 O
or EQU 2H.sup.+ +2e.sup.- .fwdarw.H.sub.2
In consequence, the hydrogen ions and the oxygen supplied from the atmospheric air to the second reaction chamber 6 are electrolyzed to form water or hydrogen. The water or hydrogen, together with the atmospheric air with the oxygen consumed in the above reaction, passes through the first suction tube 23 into the first water tank 11, where it is separated to gas and liquid. Only the water is stored within the first water tank 11, while remaining gas is discharged through the first discharge tube 11b and fed to the ambience, for example, a vegetable compartment of a refrigerator where the oxygen concentration is to be controlled.
Because of the above constitution of the conventional oxygen concentration controlling apparatus, separate direct current supply 14 and first and second water tanks 11, 12 are required to be provided separately, thus making the apparatus bulky and space-wasting. It is also disadvantageous that the oxygen concentration controlling apparatus is unable to operate if the direct current supply 14 is stopped due to some failure.
FIG. 3 is a cross section of a conventional humidity controlling apparatus disclosed, e.g., in the Japanese Patent Application Laid-Open No. 62-277126 (1987). In the drawing, a humidity controlling element 103 is constituted of first and second porous electrodes 105, 106 divided by a diaphragm 104 made of a proton conductive solid, and hermetically and rigidly circumscribed by a frame 107 made of an insulating member. The frame 107 is fixedly secured in the periphery thereof in the airtight state to an opening 102 of a sealed vessel 101 in a manner as the second porous electrode 106 of the humidity controlling element 103 is directed outside. A direct current supply 108 applies a voltage to the first and second porous electrodes 105, 106 via a lead wire 109, charging the first porous electrode 105 positively.
The operation of the above humidity controlling apparatus will be depicted now. The moisture contained in a gas in the sealed vessel 101 accompanies a reaction as follows at the interface between the first porous electrode 105 positively charged by the voltage from the direct current supply 108 and the diaphragm 104 of a proton conductive solids; EQU H.sub.2 O.fwdarw.2H.sup.+ +1/2O.sub.2 +2e.sup.-
The moisture contained in the gas of the container 101 is electrolyzed through the reaction and the oxygen molecules remain in the sealed vessel 101. The resultant hydrogen ions move towards the negatively charged second porous electrode 106 through the diaphragm 104. Then, the hydrogen ions reaching the second porous electrode 106 react at the interface between the second porous electrode 106 and the diaphragm 104 according to the following formula; EQU 2H.sup.+ +1/2O.sub.2 +2e.sup.- .fwdarw.H.sub.2 O
or EQU 2H.sup.+ +2e.sup.- .fwdarw.H.sub.2
As a result of this reaction, the hydrogen ions produce water or hydrogen which is in turn discharged to the space in touch with the second porous electrode 106. Accordingly, the humidity in the sealed vessel 101 is removed.
In the prior art, the direct current supply 108 should be provided separately from the above humidity controlling apparatus, therefore, requiring an additional space therefor. If the direct current supply 108 is troubled and stopped, the humidity controlling apparatus cannot work. Moreover, since the current is supplied only in one direction by the direct current supply 108, the apparatus functions only as a dehumidifier.